Design Team: Jon Parke and Robert Patino

December of 1998

Submitted to:

The Chemical and Biochemical Engineering Department of the University of Iowa

The significance of this report is to analyze the effects of ozone depletion in the stratosphere, summarize current steps being taken to restore the ozone, and reflect upon the impacts the ozone may have to our fragile ecosystem.

Ozone Depletion:

1. Introduction:

1. What is Ozone
2. How We Lose Ozone
3. History

2. Significance:

3. Global analysis
4. Current Investigations (modeling)
5. Restoring Ozone
6. Future Impacts
7. Summary and Conclusion

The danger of losing this critical shield is a very real concern of scientists and politicians. Humans have been the leading contributor for the decline of the ozone layer in the past several decades. The cause of this has been through manufactured products such as CFC's, HCFC's, halons, methyl bromide, carbon tetrachloride, and methyl chloroform. A CFC, or _{chlorofluorocarbon, is a man-made chemical used in aerosol propellants, cleaning agents, refrigerants, foams, and electronic parts manufacturing. CFCs were once considered wonder compounds because they were so stable in the lower atmosphere. When CFCs reach the upper atmosphere, though, CFCs can destroy ozone by liberating a chlorine atom.}

The ozone depletion process may be described as the following

Ground based measurements of Ozone were first started in 1956, in at Halley Bay, Antarctica. Satellite measurements of ozone did not start until the early 70's, and the first comprehensive worldwide measurements started in 1978 with the Nimbus-7 satellite. Nimbus-7 carried a TOMS (total ozone mapping spectrometer), and a SBUV(solar backscatter UV meter). Gases in the troposphere and lower stratosphere are sampled by weather balloons or by airplanes such as the ER-2 managed by NASA.

Chloroflourocarbons were first created in 1928 as non-toxic, non-flamable refrigerants, and were first produced commercially in the 1930's by DuPont. The first Chlorofluorocarbon was CFC-12, a single carbon with two chlorine atoms and two fluorine atoms attached to it. Today many different CFC's are produced and worldwide consumption in 1988 was estimated at over billion kilograms.

The first study that was published on CFC’s ability to catalytically breakdown Ozone in the presence of high frequency UV light was done in 1974 by M. J. Molina and F. S. Rowland. Soon afterwards, studies were conducted that estimated that the ozone layer would be depleted by CFC's by about 7% within 60 years. Based on such studies, the US banned CFC's in aerosol sprays in 1978. Soon afterwards, other countries agreed to ban CFC's in aerosols. However, industry fought the banning of CFC's because of their value in other applications. In a 1985, a field study by Farman, Gardinar and Shanklin revealed data that had been collected by the British Antartic Survey showing that ozone levels had dropped to 10% below normal January levels for Antarctica. The authors had been somewhat hesitant about publishing because Nimbus-7 satellite data had shown no such drop during the Antarctic spring.

But NASA soon discovered that the spring-time ''ozone hole'' had been covered up by a computer-program designed to discard sudden, large drops in ozone concentrations as ''errors''. The Nimbus-7 data was rerun without the filter-program and evidence of the Ozone-hole was seen as far back as 1976. Numerous studies since then have confirmed both the Antartic hole, as well as an overall global decrease in Ozone.

Further calculations and measurements show that the global ozone has decreased 2.5% from 1969 to 1986 and another shows 3% drop from 1986 to 1993 above and beyond what natural factors could account for.

Ozone chemistry is a very complicated process to understand. It is compounded by the effects of numerous side reactions that take place. An emphasis on ozone loss at the polar regions reveal a complex interplay of chemistry, dynamics, and radiation lead to conditions conducive to significant ozone loss in these regions. The sequence of events leading to the springtime depletion of ozone is initiated by the onset of polar night, when high latitude regions receive no sunlight. The inclination of the Earth's orbit causes the polar regions to experience continual darkness during their winter season. The air above the pole cools and a vortex is formed that isolates the colder region from the lower latitudes. Creation of the vortex sets the stage for the rapid depletion of ozone by catalytic cycles. A catalytic cycle is a series of reactions in which a chemical family or a particular species is depleted, leaving the catalyst unaffected.

The oxygen family is composed of ozone (O3) and atomic oxygen (O). In the presence of a chlorine atom, the net result is the conversion of an oxygen atom and ozone molecule to two molecules of oxygen (O2). Chlorofluorocarbons (CFC’s) themselves are not involved in the catalytic process. When they reach the stratosphere, they are subject to higher levels of ultraviolet radiation that decompose the CFC and release atomic chlorine. The basic set of reactions that define the catalytic cycle involving chlorine and odd-oxygen appear below:

Cl + O3 ==> ClO + O2

ClO + O ==> Cl + O2

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net result: O3 + O ===> 2O2

Genetic damage is a major environmental concern for the science community. DNA absorbs UV-B light and the absorbed energy can break bonds in the DNA. Most of the DNA breakages are repaired by proteins present in the cells nucleus but unrepaired genetic damage of the DNA can lead to skin cancers. In fact one method that scientists use to analyze amounts of 'genetically-damaging UV-B is to expose samples of DNA to the light and then count the number of breaks in the DNA. For example J.Regan's work at the Florida Institute of Technology used human DNA to find that genetically significant doses of solar radiation could penetrate as far as 9 feet into non-turbulant ocean water.

Ultraviolet radiation exists to the left of the visible spectrum and is divided into three components (UV-A, UV-B and UV-C). UV-B (290-320 wavelengths) is the most dangerous form of UV radiation that can reach ground level. Atmospheric ozone shields life at the surface from most of the harmful components of solar radiation. Chemical processes in the atmosphere can effect the level of protection provided by the ozone in the upper atmosphere. This thinning of the atmospheric ozone in the stratosphere leads to elevated levels of UV-B at ground level and increases the risks of DNA damage in living organisms.

Recent developments in frog mutations are blamed on this phenomenon. In 1997, hundreds of frogs were reported to be growing with missing or extra appendages. These cases were reported in the upper regions of the United States and southern regions of Canada. Donat Hader reports on how ozone radiation affects various aquatic life in The Effects of Ozone Depletion on Aquatic Ecosystem. There is much evidence that suggests there is much stress from UV-B rays on microorganisms such as phytoplankton.

The three main types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.

• Basal cell carcinomas are tumors that usually appear as small, fleshy bumps or nodules.
• Squamous cell carcinomas appear as nodules or as red, scaly patches.
• Malignant melanomas may appear without warning as a dark mole or other dark spot in the skin.

Several groups have been organized to assist in seeing that the global community is aware of changes in the Earth’s atmosphere. One of the leading groups is known as GAW, Global Atmosphere Watch.

GAW was established in 1989 as a coordinated system of networks of observing stations some of which began data-gathering in the1950s and includes associated facilities and infrastructure encompassing measurement and related scientific assessment activities.

The purpose and long-term goal of the GAW is to provide data, scientific assessments, and other information on the atmospheric composition and related physical characteristics of the background atmosphere from all parts of the globe.

Current investigations into Ozone depletion and how the global community can affect the change of Ozone depletion to Ozone restoration are a hot topic in the field of atmospheric research.

Stratospheric ozone depletion is a concern because the _{ozone layer in the stratosphere keeps 95-99% of the suns ultraviolet radiation from striking the earth. A number of consequences can result from increased levels of UV(ultraviolet radiation) striking the earth, including: genetic damage, skin cancer, and eye damage and damage to marine life. Increased UV radiation in the lower atmosphere, called the troposphere, can result in increased amounts of photochemical smog. Photochemical smog is already a health hazard in many of the world's largest cities.}

The decrease of stratospheric ozone was first reported in 1974 and the decrease was quickly linked to the increasing presence of a class of manmade compounds called CFC's or Chloroflourocarbons. Many countries of the world have moved to reduce the use of CFC's but because of the slow rate of air mixing between the lower and upper atmosphere it is theorized that stratospheric CFC's will stay at a significant level well into the next century.

Stratospheric ozone depletion has become very much a controversial political and economic issue as well as a complex scientific issue. _{Major and minor sources of Chlorine, and factors which affect ozone layers are still being sorted out among a great deal of media-generated excitement and misinformation; but the link between CFC's and Ozone depletion, and the major factors creating the Antarctic ozone hole, are considered by most researchers to be well established facts. Scientific models of the atmosphere are being constructed in order to assist scientists in looking for other factors in Ozone depletion, evaluate their importance and predict what may happen to our atmosphere in the future.}

Ozone Restoration is a topic that has been somewhat sensationalized by the media, and while this is possible there are other ways to improve the ozone situation that don’t include the actual production of ozone to return the ozone layer back to what it used to be decades ago. Scientists around the globe have carefully thought out most of these conventions and they are outlined in the _{Montreal Protocol on substances that deplete the ozone layer.} The Montreal Protocol is a comprehensive agenda for the reduction and finally the complete end of the production of man made ozone depleting molecules released to the atmosphere for both developed and developing countries. There are other protocols and conferences that have been useful and productive in the reduction of CFC’s and other depleting molecules such as the Kyoto Conference and the Copenhagen Amendments.

Scientific evidence shows that ozone depletion caused by human-made chemicals is continuing and is expected to persist until chlorine and bromine levels are reduced. Worldwide monitoring has shown that stratospheric ozone has been decreasing for the past two decades or more. Globally averaged losses have totaled about 5% since the mid-1960s, with cumulative losses of about 10% in the winter and spring and 5% in the summer and autumn over locations such as Europe, North America, and Australia. Since the late-1970s, an ozone "hole" has formed in Antarctica each Southern Hemisphere spring (September / October), in which up to 60% of the total ozone is depleted. The large increase in atmospheric concentrations of human-made chlorine and bromine compounds is responsible for the formation of the Antarctic ozone hole, and the weight of evidence indicates that it also plays a major role in midlatitude ozone depletion.

During 1992 and 1993 ozone in many locations dropped to record low values: springtime depletions exceeded 20% in some populated northern midlatitude regions, and the levels in the Antarctic ozone hole fell to the lowest values ever recorded. The unusually large ozone decreases of 1992 and 1993 are believed to be related, in part, to the volcanic eruption of Mount Pinatubo in the Philippines during 1991. This eruption produced large amounts of stratospheric sulfate aerosols that temporarily increased the ozone depletion caused by human-made chlorine and bromine compounds. Recent observations have shown that as those aerosols have been swept out of the stratosphere, ozone concentrations have returned to the depleted levels consistent with the downward trend observed before the Mount Pinatubo eruption.

In 1987 the recognition of the potential for chlorine and bromine to destroy stratospheric ozone led to an international agreement (The United Nations Montreal Protocol on Substances that Deplete the Ozone Layer) to reduce the global production of ozone-depleting substances. Since then, new global observations of significant ozone depletion have prompted amendments to strengthen the treaty. The 1992 Copenhagen Amendments call for a ban on production of the most damaging compounds by 1996. The figure below shows past and projected future stratospheric abundances of chlorine and bromine: (a) without the Protocol; (b) under the Protocol's original provisions; and (c) under the Copenhagen Amendments now in force.

Without the Montreal Protocol and its Amendments, continuing human use of CFCs and other compounds would have tripled the stratospheric abundances of chlorine and bromine by about the year 2050. Current scientific understanding indicates that such increases would have led to global ozone depletion very much larger than observed today. In contrast, under current international agreements, which are now reducing and will eventually eliminate human emissions of ozone-depleting gases, the stratospheric abundances of chlorine and bromine are expected to reach their maximum within a few years and then slowly decline. All other things being equal, the ozone layer is expected to return to normal by the middle of the next century.

In summary, record low ozone levels have been observed in recent years, and substantially larger future global depletions in ozone would have been highly likely without reductions in human emissions of ozone-depleting gases. However, worldwide compliance with current international agreements is rapidly reducing the yearly emissions of these compounds. As these emissions cease, the ozone layer will gradually improve over the next several decades. The recovery of the ozone layer will be gradual because of the long times required for CFCs to be removed from the atmosphere.

There is much speculation on what the global community does now and how it will impact the earth in future centuries. Some of the models attempt to predict with some scientific knowledge the outcome of our efforts now. The truth is that there is no clear cut answer as to what the future holds. There is even speculation that depletion of the ozone layer will not have as negative an impact on the earth as is widely thought throughout the scientific community _{Global Climate Information Project . There are valid arguments that efforts to reduce CFC’s and such would be detrimental to the whole economy by forcing business to constantly search for new resources and thereby putting them out of business. Only time will tell the truth.}

All of the above information and links have been compiled in order to give you a better understanding of how and why the ozone layer is being depleted and what can be done about it from a global and local effort. This website does not claim to have all of the pertinent or most recent information but does claim to give the novice an overall view of the ozone problem. Since the realization of the depletion of the ozone in 1974, research efforts have increased at an exponential rate over the past two decades. The public is more aware of the environmental problems facing the global community than back in the 1970’s. Changes in the way we live now compared to two decades ago are strong indicators that the majority of people around the globe are making efforts to reduce wastes that would be hazardous to the ozone in the atmosphere. One such example is the fast food chain McDonald’s changing from packaging that was made with CFC’s to recycled cardboard. The Kyoto treaty and Montreal Protocol are indicators that we can reduce harmful emissions and eventually phase out harmful molecules that destroy the atmosphere and seek out safer alternatives. With new information constantly being released the global community can rest assured that eventually we can solve this problem and maybe even repair some of the damage.

_{http://jwocky.gsfc.nasa.gov/}